JPH08259283A - Method for aging steel making slag - Google Patents

Abstract

PURPOSE: To efficiently age steel making slag so that expansion and disintegration are prevented. CONSTITUTION: Steel making slag is aged in an atmosphere at >=80 deg.C and >=60% relative humidity for a time (t) (hr) defined in accordance with the max. concn. (X) (%) of CaO+MgO in the slag. In the case of X<=47, t>6. In the case of 47<X<=55, t>2.25X-99.75. In the case of X>55, t>16X-85.6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for aging steelmaking slag for preventing expansion and collapse of steelmaking slag used as a roadbed material.

[0002]

2. Description of the Related Art Steelmaking slag such as converter slag is free of CaO.
, The following reaction occurs on contact with water. CaO + H ₂ O → Ca (OH) ₂ (1) When Ca (OH) ₂ is produced by the above reaction, the volume expands about twice. Therefore, when a slag containing a large amount of free CaO is used for the roadbed material, the slag gradually expands when it comes into contact with water, resulting in unevenness and cracks in the roadbed, destroying the road, and driving the vehicle. It will cause trouble.

In order to prevent expansion when using such steelmaking slag, various kinds are used so that free CaO is reduced by the reaction of the formula (1) to end expansion before using it for roadbed materials and the like. The aging process is being performed. Conventionally, atmospheric aging that stabilizes free CaO by generally crushing slowly cooled steelmaking slag, adjusting the particle size, and then stacking it in the field, leaving it for at least 3 months, and letting it hydrate with rainwater etc. Processing is being carried out. But,
Actually, in order to set the expansion coefficient to 1.5% or less, which is the expansion standard of JIS steelmaking slag, it is necessary to leave it for one year or more, which requires a lot of time and land.

As a method of shortening the aging time, Japanese Patent Laid-Open No. 61-101441 discloses a method of aging steelmaking slag by blowing steam at high temperature. In this method, since the treatment with steam at 80 to 100 ° C. is performed, the stabilization of free CaO progresses faster than at room temperature, the treatment is performed in 48 to 144 hours, and the aging treatment of steelmaking slag can be performed in a shorter time than the atmospheric aging. It can be carried out. Further, in Japanese Patent Laid-Open No. 4-175250, as a method of reducing the amount of steam in steam aging, a plurality of thermometers are embedded in the slag layer, the temperature is raised to 100 ° C., and then the steam is stopped to set the temperature to a lower limit temperature (95 ° C.). Then, a method of repeating flowing steam is disclosed.

[0005]

Problems to be Solved by the Invention JP-A-61-1014
The method disclosed in Japanese Patent No. 11 has an effect that the aging process can be performed in a shorter time than the atmospheric aging. However, regardless of the type and composition of slag, the aging time of flowing steam is 48 hours or more, and in reality, the steam is wasted for slag that can be aged in less than 48 hours. become. Further, in Japanese Patent Laid-Open No. 61-101411, after the steam is blown for 48 hours or more, the supply of steam is stopped, and the so-called curing is carried out by leaving it for 7 days. I needed a long period of more than 9 days for aging.

Further, in the method disclosed in Japanese Patent Laid-Open No. 61-175250, aging may be delayed during the temperature decrease of 10 ° C. because the steam is intermittently flown, and a plurality of thermometers may be used. For the purpose of control, if steam is caused to flow on the basis of the thermometer having the lowest temperature, steam may be excessively used. An object of the present invention is to provide a steam aging method for steelmaking slag, which can reduce the steam basic unit (steam amount per ton of slag) and can shorten the treatment time.

[0007]

The present invention was developed to solve the above problems, and in a method for aging steelmaking slag, the temperature is 80 ° C. or higher and the relative humidity is 60%.
Provided is a method for aging steelmaking slag, which is characterized by maintaining a constant aging time in the above atmosphere. In this case, the aging time t (hr) is set to the slag composition X
= (% CaO) + (% MgO) according to the maximum concentration, the range may be defined by the following formula.

When X ≦ 47: t> 6 47 <X ≦ 55: t> 2.25X−99.75 When 55 <X: t> 16X−856 However, the above “according to the maximum concentration of the composition X is satisfied. Means "(% CaO) + (% Mg for slag with non-uniform slag composition."
It means that the aging time is determined by the above equation using the value of the composition X having the highest O) concentration.

Further, according to the present invention, the steam flow rate is raised and aged at a flow rate of 10 kg / h or more per ton of slag until the temperature difference between the temperature of the entire slag and the steam brought into contact with the slag is 5 ° C. or less, and thereafter. It is preferable to reduce the steam flow rate and maintain the above constant aging time.

[0010]

[Operation] When steam aging is performed, steelmaking slag exposed to an atmosphere of steam has a temperature of 80 ° C and a relative humidity of 60%.
It is necessary to maintain the above atmosphere. If the temperature is lower than 80 ° C., the progress of aging becomes extremely slow, which is uneconomical. 230 g of slag whose particle size is adjusted to 4.75 to 13.2 mm,
A press-molded product having a diameter of 50 mm and a height of about 40 mm at a pressure of ² ton / cm ² was placed in a container and held in a thermo-hygrostat under predetermined conditions, and the expansion coefficient was measured. As for the expansion rate, a dial gauge was attached, the expanded length was recorded every 24 hours, and the percentage of expansion relative to the original length was determined. The expansion coefficient measurement results after the converter slag having a final expansion coefficient of 3.75% was held for 240 hours in an atmosphere in which the relative humidity was variously changed at 80 ° C., 70 ° C., and 60 ° C. are shown in FIG.
It was shown to. When the temperature was 80 ° C. and the relative humidity was 60% or more, the expansion rate of the slag reached 3.3% or more, and almost satisfactory results were obtained. At temperatures of 70 ° C and 60 ° C, the aging effect is insufficient, and even at temperatures of 80 ° C, the relative humidity is 60%.
Less than is not enough. According to FIG. 1, the relative humidity in the atmosphere needs to be at least 60% or more at 80 ° C. The higher the relative humidity, the better, and at a temperature of 80 ° C., it is preferably 80% or more.

Next, the component X in the steelmaking slag = (% Ca
The effect of (O) + (% MgO) on aging was investigated. 10 kg each of converter slag, desiliconization slag, dephosphorization, and de-S slag were adjusted to the particle size of the roadbed material, and then the time was changed and the material was kept in a steam atmosphere. Then, JIS water immersion expansion test was performed. Compared with converter slag, de-siliconization slag and dephosphorization de-S removal slag, which are the hot metal pretreatment slag, have different appearance, color and shape even if they have the same charge, and they are separated to analyze the chemical composition. Then there was a big difference. Therefore, the separated ones were each aged with water vapor, and a JIS water immersion expansion test was carried out. X = (% CaO) + even if the composition is different for the same charge
It was possible to sort by (% MgO).

Therefore, when steam aging a large amount of slag for one charge and several charges, the steam aging time is based on the highest (% CaO) + (% MgO) in the entire slag. I need to decide. As a specific method for determining the time, a large number of things having different appearances in one charge are sampled, the highest value of (% CaO) + (% MgO) is obtained in advance, and the same concentration is used as a reference. The steam aging time for the slag that is being treated may be set.

FIG. 2 shows the expansion coefficient of slag after aging when various slags with X = (% CaO) + (% MgO) of 40 to 65% were aged under the conditions of a temperature of 80 ° C. and a relative temperature of 60%. Is a plot of the time taken to be less than 1.5%. As shown in FIG. 2, it was found that as X increases, the time required for aging becomes longer and aging becomes difficult. In particular, when X exceeds 60%, the aging time becomes extremely long.

Summarizing these results, it is necessary to set the aging time t (hr) at which the expansion coefficient of the slag is less than 1.5% as follows. When X ≦ 47: t> 6 47 <X ≦ 55: t> 2.25X−99.75 55 <X: t> 16X−856 The aging time t (hr) here is the entire slag. The time after the temperature difference between the temperature of the steam flowing at 80 ° C. or higher and the temperature of the steam flowing at 5 ° C. is 5 ° C. or lower. In this case, no curing time is required after stopping the steam.

In order to age the free CaO and the like in the steelmaking slag, the piled slag is supplied with steam from its bottom to age it. It takes time depending on the required sensible heat of the slag, the heat transfer mechanism, and the steam flow rate. In addition, aging treatment of the whole piled slag requires a certain time or more in contact with water vapor, depending on the properties of the slag. In the conventional method of flowing a constant flow rate of steam for a predetermined time, it takes too much time to raise the piled slag, and conversely, when the temperature of the slag is close to the steam temperature, the heat transfer amount decreases and the steam amount becomes excessive and wasteful. become. FIG. 3 shows the relationship between the flow rate of water vapor and the time for the temperature of the slag apex to reach 100 ° C. when the height of the piled slag is 2 m. As is clear from FIG. 3, as the amount of water vapor increases during heating, the heating time is shorter and the processing time can be shortened. After raising the slag temperature to a temperature close to the temperature of water vapor, it is preferable to reduce the water vapor flow rate as much as possible to reduce the steam consumption rate. However, if the flow rate of steam is reduced too much, the temperature of the slag layer will drop, and this must be avoided.

In the present invention, when heating the piled slag, the steam flow rate is 10 kg / h per ton of slag.
Because of the above, the temperature rises rapidly, and at a height of 2 m, the temperature can be raised to 100 ° C. within 16 hours. Further, after the temperature rise, the thermal conductivity of the slag is low, and the heat retention effect of the piled slag is high, so the temperature drop is very slow. Therefore, to keep the whole piled slag at a high temperature close to 100 ° C., a small amount is needed. You can use steam. FIG. 4 shows an example of temperature changes at a position 200 mm below the slag top when various amounts of slag piled up at a height of 2 m in a steam aging pilot plant are supplied with a small amount of steam after reaching a temperature close to 100 ° C. It is shown. 0.3 per ton of slag
It is understood that it is sufficient to supply steam of kg / h or more.

In the present invention, the entire piled slag is 10
When the temperature reached close to 0 ° C., the flow rate was reduced to the amount of water vapor that can be kept at a high temperature to eliminate the waste of water vapor. The steam flow rate for heat retention depends on the type of slag, the particle size,
It can be appropriately determined by referring to experimental values according to the shape of the pile, the surrounding environment, the outside air temperature, and other conditions.

[0018]

EXAMPLES Examples of the present invention will be described together with comparative examples. The steam aging equipment consists of multiple steam pipes arranged in parallel and embedded in the gravel layer. The steam pipe is provided with steam outlets at regular intervals. Steam aging of the steelmaking slag was performed by stacking piles of slag adjusted to a predetermined grain size on the gravel layer in which the steam pipe was buried, and blowing out steam from the pipe. Table 1 shows the chemical composition of the treated slag. Steam aging treatment was performed on the converter slag, desiliconization slag, and dephosphorization desulfurization slag. The amount of slag treated once was 100 to 150 tons, and steam having a temperature of 100 ° C. at the pipe outlet was used. Table 2 shows the steam aging treatment conditions and the JIS water immersion expansion test results after the treatment.

In the example, since the vapor flow rate during the temperature increase was increased, the temperature increase of the piled slag was completed in a short time. Therefore, the time of the entire processing is 50 to 50
It was shortened to 70%. Almost 10 piles of slag
After reaching 0 ° C, change the steam flow rate to 0.3 per ton of slag.
It was kept warm by squeezing it to ~ 1 kg / h. Therefore, it is possible to reduce wasteful water vapor, and to reduce the water vapor consumption rate to 60 to 90% of the comparative example with the same slag. In the comparative example, not enough steam was supplied at the beginning of the treatment, but a relatively large amount of steam was supplied until the end, so it took more than one day to heat up the piled slag, and then piled up after the temperature was raised. A large amount of water vapor is released into the atmosphere after passing through the slag, and there is much waste of water vapor. Regarding the water immersion expansion rate, when comparing the same type of slag, a low value which is substantially equal to or lower than the reference value was obtained in the example and the comparative example.

In the present invention, no special equipment modification was required. According to the method of the present invention, the aging treatment of steelmaking slag for roadbed materials can be carried out in a short time with a small amount of water vapor.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

According to the present invention, when the steelmaking slag is subjected to the steam aging treatment, 10 kg / h per ton of slag is heated during the temperature rising.
Since a large amount of steam as described above is flowed, the temperature rise time can be shortened, and after the piled slag has risen to a temperature almost close to the steam temperature, the steam flow rate required for heat retention, for example, per ton of slag. Since it was reduced to about 0.3 kg / h, the steam basic unit could be reduced to 60 to 90% of the conventional amount, and the processing time could be shortened. According to the method of the present invention, it is possible to achieve both economic efficiency by shortening the processing time and reducing the basic unit of water vapor, complete stabilization of free CaO, and treat slag suitable for roadbed materials.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the temperature and relative humidity of the atmosphere and the expansion coefficient of unaged slag.

FIG. 2 is a graph showing the relationship between (% CaO) + (% MgO) and aging time.

FIG. 3 is a graph showing the relationship between water vapor flow rate and temperature rise time.

FIG. 4 is a graph showing the relationship between water vapor flow rate and temperature drop.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisahiro Matsunaga 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Technical Research Laboratory, Kawasaki Steel Co., Ltd. (72) Masato Kumagai 1 Kawasaki-cho, Chuo-ku, Chiba Kawasaki Steel Co., Ltd. Technical Research Institute (72) Inventor Keiji Taguchi 1st Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Kawasaki Steel Co., Ltd. Technical Research Laboratories (72) Inventor Sato Yukio, Kawasaki-cho, Chuo-ku, Chiba Stock Company Chiba Factory

Claims (3)

[Claims] 1. A method for aging a steelmaking slag, which is characterized by holding for a certain aging time in an atmosphere having a temperature of 80 ° C. or more and a relative humidity of 60% or more. 2. The steelmaking according to claim 1, wherein the aging time t (hr) is set in a range defined by the following formula according to the maximum concentration of the slag composition X = (% CaO) + (% MgO). Aging method for slag. When X ≦ 47: t> 6 47 <X ≦ 55: t> 2.25X-99.75 55 <X: t> 16X-856 3. The difference between the temperature of the entire slag and the temperature of water vapor is 5
The steam flow rate is 10k per ton of slag until the temperature drops below ℃
The method for aging steelmaking slag according to claim 1, wherein the temperature is raised and aged at a flow rate of g / h or more, and then the flow rate of steam is reduced to maintain a constant aging time.